What is the ruling on combining Dhuhr and Asr, and Maghrib and Isha prayers when picnicking in the desert at a distance of 35 km with cold weather and carrying water, and what are the regulations for combining prayers?

Going for a short walk and experiencing usual cold weather does not permit combining prayers. The five daily prayers have specific times legislated by Sharia (definition), and it is not permissible to delay or advance them except with a legitimate excuse. The Hanbalis permitted combining the Maghrib and Isha prayers only due to severe cold winds, not merely cold weather. The same applies to snow, hail, ice, and mud.